The bats/notes are out of sync with the music track.

Depending on the device, the bats and the music may not be in sync.

To fix this problem, please use the “Audio Delay” slider, which you can find in the options menu.

If the bats pass the tower too early (i.e. before their correct time in the track), try a lower (more negative) value.
If the opposite is the case, try positive values.
Find out which value works best for your device.